Relative flare amplitude versus flare duration for the 8 stars with reliable P_rot that have no PM companion. The orange and turquoise lines are linear fits performed in different SpT ranges as indicated in the legend. Left panel: normalized peak flare amplitude. Right panel: peak flare luminosity amplitude. Relations from Hawley et al. (2014) and Raetz et al. (2020) are overplotted for comparison; see Sect. 4.5 for details.